Incremental Load using qvd files Incremental Load Differential
- Slides: 18
Incremental Load using qvd files
Incremental Load • Differential Load • Delta Load
Incremental Load only the new or changed records from the database. The rest should already be available, one way or another.
Incremental Load • Load new data from Database table (slow, but few records) • Load old data from QVD file (many records, but fast) • Create new QVD file • Procedure must be repeated for each table
Different DB-changes If source allows … 1) Insert only. (No Update or Delete) 2) Insert and Update. (No Delete) 3) Insert, Update and Delete.
1) Insert only • Can be any DB • Loads INSERTed records • Needs the field Modification. Date
1) Insert only QV_Table: SQL SELECT Primary. Key, X, Y FROM DB_TABLE WHERE Modification. Time >= #$(Last. Exec. Time)#;
1) Insert only QV_Table: SQL SELECT Primary. Key, X, Y FROM DB_TABLE WHERE Modification. Time >= #$(Last. Exec. Time)#; Concatenate LOAD Primary. Key, X, Y FROM File. QVD;
1) Insert only QV_Table: SQL SELECT Primary. Key, X, Y FROM DB_TABLE WHERE Modification. Time >= #$(Last. Exec. Time)#; Concatenate LOAD Primary. Key, X, Y FROM File. QVD; STORE QV_Table INTO File. QVD;
1) Insert only QV_Table: SQL SELECT Primary. Key, X, Y FROM DB_TABLE WHERE Modification. Time >= #$(Last. Exec. Time)# AND Modification. Time < #$(Beginning. This. Exec. Time)#; Concatenate LOAD Primary. Key, X, Y FROM File. QVD; STORE QV_Table INTO File. QVD;
2) Insert and Update • Can be any DB • Loads INSERTed and UPDATEd records • Needs the fields Modification. Date and Primary. Key
2) Insert and Update QV_Table: SQL SELECT Primary. Key, X, Y FROM DB_TABLE WHERE Modification. Time >= #$(Last. Exec. Time)#; Concatenate LOAD Primary. Key, X, Y FROM File. QVD WHERE NOT Exists(Primary. Key); STORE QV_Table INTO File. QVD;
2) Insert, Update and Delete • Can be any DB • Loads INSERTed and UPDATEd records • Removes DELETEd records • Needs the fields Modification. Date and Primary. Key • Tricky to implement
3) Insert, Update and Delete QV_Table: SQL SELECT Primary. Key, X, Y FROM DB_TABLE WHERE Modification. Time >= #$(Last. Exec. Time)#; Concatenate LOAD Primary. Key, X, Y FROM File. QVD WHERE NOT EXISTS(Primary. Key); Inner Join SQL SELECT Primary. Key FROM DB_TABLE; STORE QV_Table INTO File. QVD;
3) Insert, Update and Delete List. Of. Deleted. Entries: SQL SELECT Primary. Key AS Deleted FROM DB_TABLE WHERE Deletion. Flag = 1; QV_Table: SQL SELECT Primary. Key, X, Y FROM DB_TABLE WHERE Modification. Time >= #$(Last. Exec. Time)#; Concatenate LOAD Primary. Key, X, Y FROM File. QVD WHERE NOT Exists(Primary. Key) AND NOT Exists(Deleted, Primary. Key); Drop Table List. Of. Deleted. Entries; STORE QV_Table INTO File. QVD;
Last. Execution. Time & Error handling Let This. Exec. Time = Reload. Time(); { Load sequence } If Script. Error. Count = 0 then Let Last. Exec. Time = This. Exec. Time; End If
Final Script Let This. Exec. Time = Reload. Time(); QV_Table: SQL SELECT Primary. Key, X, Y FROM DB_TABLE WHERE Modification. Time >= #$(Last. Exec. Time)# AND Modification. Time < #$(This. Exec. Time)#; Concatenate LOAD Primary. Key, X, Y FROM File. QVD WHERE NOT EXISTS(Primary. Key); Inner Join SQL SELECT Primary. Key FROM DB_TABLE; If Script. Error. Count = 0 then STORE QV_Table INTO File. QVD; Let Last. Exec. Time = This. Exec. Time; End If
Summary • Incremental Load possible for… • • • Insert only. (No Update or Delete) Insert and Update. (No Delete) Insert, Update and Delete.
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